More than 60 ruling Liberal Democratic Party lawmakers established a study group Monday aiming to strengthen Japan's control of the Senkaku Islands and surrounding waters in the East China Sea claimed by China.
The move came as China is intensifying maritime activities near the Japan-controlled islands by sending patrol boats into and near Japanese territorial waters around the uninhabited group of islets.
On Monday, four Chinese vessels were observed sailing in the territorial waters around the Senkakus, according to the Japan Coast Guard. Chinese ships last entered the waters on Aug. 9.
At the group's first meeting, Tomomi Inada, the LDP's acting secretary-general and a former defense minister who leads the group, said China's escalating assertiveness is threatening Japan's administration of the islands.
She called for legislation that would oblige the government to resume conducting research missions on the islands' ecosystem and marine resources after a decadeslong hiatus.
The last large-scale survey led by the Japanese government was undertaken in 1979.
A former government official who led the 1979 survey of the islands said in the meeting that building a heliport or a lighthouse as an initial step to enhance Japan's effective control is technically possible.
But setting up a harbor or a refuge for fishermen as requested by residents of nearby islands would be difficult, as there are no suitable areas on the islands, the official said.
The Senkakus, called Diaoyu in China, have long been at the center of conflict between the two countries. The Japanese government insists the islands are an inherent part of its territory in terms of history and based on international law. Taiwan also claims them.
Concern is growing in Japan that the end of a China-established suspension of fishing in areas of the East China Sea near the islands on Sunday will bring an inordinate number of government and fishing vessels into or near the area.
In August 2016, a group of China Coast Guard vessels and as many as 300 fishing boats crowded around the islands despite a flurry of high-level protests from Tokyo.
Through early this month, Chinese patrol vessels had been spotted near the Senkakus for 111 consecutive days, the longest streak since Japan put the islets under state control in 2012.